1. Field of the Invention
The present invention relates to fail-safe and other control mechanisms for a remote controlled telephone answering device.
2. Description of the Prior Art
A particularly useful feature of some telephone answering devices is the ability of the user to have his messages played out automatically by remote control. Typically, when the user is away from his home or office and desires to hear his messages, he will call his own telephone number. When the device answers the telephone automatically, the user will transmit a beep tone via the telephone line which will cause the answering device to switch into a remote playout mode. The tape containing the recorded incoming messages is quickly rewound, and then set to the forward direction to play back the recorded messages via the telephone line. When all of the messages have been played out, the device is returned to the normal answering mode.
Various approaches have been used to control termination of the remote playout cycle. For example, in the apparatus of U.S. Pat. No. 3,067,289 to Zimmermann, an integrating timer is mechanically coupled to the incoming message recorder. This timer provides an index of the total elapsed recording time. When the tape is rewound in response to receipt of a remote control signal, the integrating timer retains its prior position. Then, as the recorded messages are played out to the user, a cam is mechanically advanced. When the message playout time equals the elapsed recording time stored by the integrating timer, the cam closes a microswitch to terminate the playout operation.
In a prior art system of the type just described, a complex mechanical arrangement is required to function as the integrating timer. Other prior art devices utilize different types of mechanical timers to control the playout duration of the recorded messages. Such techniques do accomplish the intended function, but require complex mechanical arrangements which add substantially to the cost of the device. Such methods are thus inapplicable to low cost telephone answering devices.
An alternative approach, not requiring an integrated timer, is to have the user terminate the playout cycle after he has heard all of the messages. This is accomplished by having the user send a second beep tone over the telephone line. The tone is detected by the device and used to terminate the playout operation. This technique can be implemented at low cost. Typical control circuitry for such a low cost, remote controlled telephone answering device is disclosed in the inventor's copending U.S. patent applications Ser. Nos. 897,279, filed Feb. 21, 1978 and 892,326, filed Mar. 31, 1978 now U.S. Pat. No. 4,126,763.
A problem may arise in the use of such a remote controlled telephone answering device in the event that the second beep control signal is not received. This may occur if the user forgets to send the second beep tone, or if for any reason the telephone connection is broken between the user and the answering device while the messages are being played out. Such an interrupted connection may occur if the user inadvertently hangs up before sending the second beep tone. It may also occur because of an inadvertent disconnect in the telephone transmission facilities.
If the second beep tone is not received, the telephone answering device will continue to run in the remote playout mode. The incoming message tape will continue to be wound onto the takeup reel. Previously recorded messages, if any, will continue to be transmitted to the telephone line, but of course will not be heard by the user if the circuit has been interrupted. Eventually, substantially all of the message tape will be wound onto the takeup reel.
Generally, a "fail-safe" circuit is provided to disable the telephone answering device when all of the message tape has been wound onto the takeup reel and no more is available for recording subsequent calls. This condition may occur normally if the maximum number of calls are received prior to the user playing back these messages, either under remote control or by using the built-in playback capability of the device. The condition also may occur as described above, in the event of remote controlled playback without receipt of the second beep control signal.
The "fail-safe" mechanism may take the form of a switch circuit which disables the telephone answering device and leaves the telephone line in an off-hook condition. As a result, a subsequent caller will get a busy signal. Of course, his call will not be answered. Alternatively, the mechanism may disconnect power from the answering device so that the caller hears a ring tone, but the call goes unanswered. Such "fail-safe" mechanisms present a serious disadvantage in a remote controlled playback system of the type described. If the "fail-safe" mechanism should be actuated as a result of non-receipt of the second beep control signal, the resultant answer disabling condition will totally prevent the user from subsequently remotely resetting the device to the normal answering mode. If the user again tries to call his own number, his call will not be answered. Thus the user will have to return to the physical location of the answering device and rewind the message tape under manual control. Obviously, this is a severe handicap for a user who plans to be away from his home or office for long periods of time.
A principal object of the present invention is to overcome this shortcoming of the prior art, and to provide a remote controlled telephone answering device which can be subsequently remotely actuated and returned to the normal answering mode even after all of the incoming message recording tape has been wound onto the takeup reel and the "fail-safe" circuit has been activated. To this end, the "fail-safe" circuit of the present invention does not cause an off-hook condition to occur, but rather modifies the ring response time of the ring detector so that a very large number of rings, typically 20 to 25, are required to effectuate automatic answering. A typically caller will hang up before this number of rings occurs. The user, however, recognizing the situation, can allow the requisite number of rings to occur so that his call will be answered. The user can then transmit beep control signals over the telephone line so as to cause rewinding of the incoming message tape and return of the device to the answer mode. This will condition the device to answer subsequent incoming calls in a normal manner. An additional object of the present invention is to provide appropriate control circuitry to accomplish such operation.
The electromechanical arrangements for accomplishing remote controlled rewind of the incoming message tape may be of the type disclosed in the above-identified co-pending applications of the inventor, or may be of the type disclosed in the inventors's U.S. Pat. No. 4,104,487, filed Dec. 13, 1976. However, it is another object of the present invention to provide yet a different type of cam-actuated mechanism for accomplishing such automatic rewind in a remote controlled telephone answering device. The inventive mechanism, in response to the receipt of a beep control signal, positions the tape drive motor into the rewind position so as to rewind the incoming message tape. The mechanism senses the completion of rewind, and thereafter returns the tape drive motor to the forward position so as to enable remote playout of the previously recorded messages. During the rewind operation, regulation of the voltage to the tape drive motor may be inhibited so that the motor will operate at maximum speed. In this regard, the present invention may be used in conjunction with the voltage regulator circuitry disclosed in the inventor's co-pending U.S. patent application Ser. No. 641,551, filed Dec. 17, 1975. Further to reduce the cost of the device, the present invention may be used in conjunction with an "all-plastic" type of construction such as that disclosed in the applicant's co-pending U.S. patent applications Ser. No. 766,898, filed Feb. 9, 1977 now U.S. Pat. No. 4,118,602 and 874,361, filed Feb. 2, 1978. However, the present invention may be used by itself or in conjunction with other telephone answering mechanisms, and need not necessarily be used with any of the circuits or devices disclosed in any of the inventor's other U.S. patent applications or patents identified hereinabove.